1. Field Of The Invention
This invention relates to casing cementers for use in oil and gas wells, and more particularly, to a casing cementer which is opened and closed by rotation of a positioning tool and includes a means for limiting torque applied thereto.
2. Description Of The Prior Art
Currently, most casing cementers used in operations for cementing well casing utilize reciprocating motion to open and close the cementer. Examples of such devices include the Halliburton FO Cementers which have a sliding sleeve therein and are generally disclosed in U.S. Pat. No. 3,768,562, assigned to the assignee of the present invention. Collet fingers on the cementer hold the tool closed (or open) until a positioning tool is inserted to actuate the sleeve in the cementer. The positioning tool uses fingers to latch into the cementer and open and close the sleeve by reciprocation. Similar devices include the Halliburton FO Packer Collar and Halliburton FO Frac Tool.
The FO Cementers have worked well, but occasionally difficulties occur with other tools used with them. Swab cups sometimes swell out when passing through such cementers, and this can cause tearing of the cups or undesired opening of the cementer. On some other tools, slips may open when passing through the cementer which can cause the tools to stick and can also result in undesired opening or closing of the cementer.
Another factor is that the FO Cementer and the positioning tool therefor are relatively long and machining of the components is somewhat complicated. Reduction in costs is desirable in many instances.
Accordingly, there is a need for a smaller cementer which requires less machining of components and one which is less susceptible to inadvertent opening when some tools are passing therethrough. The present invention meets this need by providing a cementer which is opened by rotation of a positioning tool rather than by reciprocation.
A previously known cementer which uses rotation for opening and closing is the TAM port collar manufactured by TAM International, Inc. In this device, a tool is run in on a work string to operate the port collar. The tool has spring-loaded dogs to latch into an inner sleeve in the port collar, allowing the collar to be opened and closed with rotation. The inner sleeve in the TAM port collar has an inside diameter less than that of the casing string so that when the operating tool is run into the casing, an indication is given to the operator at the surface when the latching dogs engage this smaller inside diameter so that the operator will know that the tool is positioned. Having a smaller diameter in the cementer is undesirable in many cases, so there is a need for a cementer opened by rotation which has a large diameter. The present invention solves this problem by providing a cementer with a valve sleeve which has an inside diameter no less than that of the casing string.
With the operating tool in the TAM port collar, there is no means for limiting torque. Therefore, excessive torque may be applied to the port collar inner sleeve, which may cause damage to the operating tool and/or the port collar. Therefore, there is a need for a casing cementer opened by rotation wherein the operating tool has a means for limiting torque. The present invention provides such a solution to this problem.